Garage Sale

I took four tires to a friend’s garage sale and was asking $35 apiece. I needed to step away for a bit so I asked him to watch them for me.
“Sure,” he said, “but just in case someone offers less, how low are you willing to go?”
“Try for more, but I will accept $20 each,” I said, and left.
When I returned, my tires were gone. “How much did you get for them?” I asked excitedly.
“Twenty dollars each.”
“Who bought them?”
“I did!”